BEIRUT — The Syrian army has recaptured the northern rebel stronghold of Idlib near the Turkish border, a major base that military defectors had held for months, a pro-government newspaper and an activist group said Tuesday.

The three-day operation to capture Idlib gives the regime some momentum as it tries to crush the armed resistance. But it also fed international condemnation. The Arab League chief said the regime’s killing of civilians amounts to crimes against humanity and he called for an international inquiry.

New York-based Human Rights Watch said troops have planted land mines near its borders with Turkey and Lebanon along routes used by people fleeing the violence and trying to reach safety in neighboring countries. HRW said its report was based on accounts from witnesses and Syrian deminers and that the land mines have already caused civilian casualties.

“Any use of anti-personnel land mines is unconscionable,” said Steve Goose of Human Rights Watch. “There is absolutely no justification for the use of these indiscriminate weapons by any country, anywhere, for any purpose.”

In November, a Syrian official and witnesses told The Associated Press that Syria planted land mines along parts of its border with Lebanon. The official claimed at the time that the mines aimed to prevent arms smuggling.

HRW quoted a former Syrian army deminer as saying that in early February, he visited the border town of Hasanieih and found land mines planted “between the fruit trees three meters (yards) from the border in two parallel lines, each approximately 500 meters (yards) long.”

HRW also quoted a resident of the border town of Kherbet al-Joz as saying that for 20 days, until March 1, he saw some 50 soldiers accompanied by two large military vehicles putting land mines starting from Kherbet Al-Joz toward two other villages. Both Kherbet al-Joz and Hasanieih border Turkey in the north.

Fresh from a monthlong campaign that drove rebels out of another key base in central Homs, Assad’s forces launched a siege on the city of Idlib three days ago. The city largely had been under control of hundreds of fighters for the rebel Free Syrian Army.

The Al-Watan daily and the Britain-based Syrian Observatory for Human Rights said government troops were in control of Idlib on Tuesday. The Observatory said the army was still facing some resistance pockets in three Idlib areas, including the central neighborhoods of Dubait and Bustan Ghanoum.

Idlib, a predominantly Sunni city of some 150,000 people located about 100 miles (160 kilometers) north of Homs, was among the first to fall in the hands of army defectors last summer. Rebels were in control of a large parts of the city in the past months with troops present in some areas.

There was no official confirmation of its capture and calls to the area were not going through. Witnesses said this week that army defectors in the city have been running out of ammunition.

Many feared the offensive in Idlib could end up like the regime’s campaign against the rebel-held neighborhood of Baba Amr in the city of Homs. Troops besieged and shelled Baba Amr for almost a month before capturing it on March 1, after hundreds of civilians were killed.

Arab League chief Nabil Elaraby said it would not be ethical or moral to allow those behind the killings in the cities of Homs and Idlib to get away with their crimes.

“There must be an impartial international inquiry into what is happening to uncover those responsible for these crimes to face justice,” he said in Cairo.

In northern Syria, the Observatory and another activist group, the Local Coordination Committees, reported intense clashes between government troops and rebels in the town of Maaret al-Numan, in Idlib province, on Sunday night.

The LCC said four civilians were killed in the government shelling while the Observatory said 10 soldiers were killed when their checkpoint was attacked by defectors.

Both groups said that bodies of six people were found Tuesday near the village of Maaret Shoureen in Idlib province. The LCC said Syrian troops stopped the six who were in an ambulance, ordered them out of the vehicle and then shot them dead. Two of the people from the ambulance had been wounded in the shelling earlier.

Earlier this year, Assad’s forces began major military operations to retake rebel-held areas, starting with an attack that recaptured several suburbs of the capital Damascus and followed by the offensive in Homs. The operation in Idlib province, of which Idlib is the provincial capital, is the latest.

An amateur video posted online Tuesday but was said to have been taken three days ago showed several army tanks from a distance in a major street around Idlib. An activist was heard saying that tanks are deploying around Idlib in preparation to storm it.

The U.N. refugee agency said 230,000 Syrians have fled their homes since the uprising against Assad’s regime began last year. The U.N. says more than 7,500 people have been killed in the past 12 months.

Panos Moumtzis, the UNHCR’s coordinator for Syria said 30,000 people have already fled to Turkey, Lebanon and Jordan and “on a daily basis hundreds of people are still crossing into neighboring countries.”

Moumtzis said at least 200,000 people were also displaced within the country, according to the Syrian Arab Red Crescent.

Assad has made a series of gestures toward reform to try to allay the crisis, but his opponents say his efforts are too little, too late. On Tuesday, he set nationwide parliamentary elections for May 7. The vote was initially to take place in March but was postponed after last month’s referendum on the country’s new constitution that allowed new political parties to run.

In the past, the National Progressive Front, which includes Assad’s ruling Baath party and 11 other closely associated groups, had dominated elections and the 250-member legislature.

However, it’s unclear how an election can take place as a deadly spiral of violence continues to shake Syria.